Shielded color grid structure for cathode-ray tubes



March 20, 1956 c. s. NUNAN ET AL 2,739,263

SHIELDED COLOR GRID STRUCTURE FOR CATHODE-RAY TUBES 3 Sheets-Sheet 1Filed June 21, 1954 GF/D CO/UDl/CTURS 440/1450 w WWW a mwm N z W \Q Zm mm0 6 E R Y B a GBGR/Q E I E- I March 20, 1956 c s NUNAN E AL SHIELDEDCOLOR GRID STRUCTURE FOR CATHODE-RAY TUBES Filed June 21, 1954 3Sheets-Sheet 2 INVIENTOR. Fen/7 ,Zaph/ropoa/os Cry/y 5 Nana/1 March 20,1956 c. s. NUNAN ET AL 2,739,263

SHIELDED COLOR GRID STRUCTURE. FOR CATHODE-RAY TUBES Filed June 21, 19543 Sheets-Sheet 3 IN VEN TOR.

SHIELDED COLOR G STRUCTURE FOR CATHODE-RAY TUBES Craig S. Nunan,Berkeley, and Renn Zaphiropoulos, Oakland, Califi, assignors toChromatic Television Laboratories, Inn, New York, N. Y., a corporationof California Application June 21, 1954, Serial No. 438,238

Claims. (Cl. 315-14) The present invention relates to cathode-ray tubesof a type adapted to efiect the reconstitution of polychrome images.More particularly, the invention relates to a color structure for suchcathode-ray tubes which is readily adaptable to shielding and hence canbe made to possess relatively low radiation characteristics.

Cathodeay tubes having a grid of essentially parallel wires locatedadjacent to a striped phosphor screen are now known in the art. Such astructure may in some cases serve as one component of an electron lenssystem to focus the beam electrons into a pattern of thin linesnominally registered with the discrete phosphor areas of the screen, asis exemplified by Ernest 0. Lawrence in his United States Patent No.2,692,532 granted October 26, 1954.

One type of cathode-ray tube incorporating the above principle (whichmay be termed post-deflection-iocusing) is designed with a relativelylarge number of narrow component-color phosphor strips laid down in apredetermined sequence to form a screen, or target electrode. Thesephosphor strips luminesce, when impacted by the cathode-ray beam, invarious component colors of the image to be synthesized. Purely as anexample, the order in which the phosphor strips are laid down may bered, green, blue, green, and so on, bearing in mind that the color of aphosphor as used herein relates to the color of the light emittedtherefrom which reaches the eye of an observer. Anelectrically-conductive coating overlies the phosphor strips, and isproduced in some preferred manner such as by aluminization.

In order that the path of an electron arriving at the phosphor screenfrom the cathode emitter may be controlled in a selective manner in thevicinity of the target, a grid assembly is located adjacent to thephosphor screen and, with the latter, comprises a color structure of atype to which the present invention is related. Such a grid is formed ofa large number of wires, or linear conductors, extending in the samegeneral direction as the phosphor strips, and lying in the path ofelectrons directed to the target electrode from the electron gun of thecathode-ray tube. The wires of the grid assembly are electron-opticallyrelated to the phosphor strips so that, in this electron-optical sense,there is a wire aligned with each blue strip, and similarly a wirealigned with each red strip. It should be borne in mind that thiselectron-optical ali nment incorporates whatever spacing corrections arenecessary to compensate for variations introduced into the tubeoperation by changes in the instantaneous angle of impingement of thecathode-ray beam as it scans the target, and also by changes indeflection sensitivity at portions of the target electrodeassymetrically located with respect to the tube axis. However, thesecorrections form no part of the present invention, and are mentionedmerely as an aid in understanding the operation of a tube of the natureset forth. All of the wires associated with the red strips are connectedto a common 7 terminal, while the blue wires are similarly joinedtogether electrically.

2,739,263 Patented Mar. 20, 1956 drical lenses) cause the beam electronsarriving at the wire grid from the electron gun of the tube to form afine line structure on the phosphor target. It will be appreciated thatthe particular scanning operation by means of which the beam electronsare caused to trace a raster at the plane of the grid wires has nodirect geometrical relationship to the actual line structure developedon the target electrode, the latter being determined solely by theconfiguration of the wires of the grid assembly.

Inasmuch as the grid wires, as stated above, are electron-opticallyaligned with the phosphor strips, a zero potential difference betweenthe red and blue terminals of the grid will result in the beam electronsundergoing a focusing action alone, and hence these electrons may becaused to impinge the target within the boundaries of a particular stripsuch as green. If the conductors associated with the red strips are maderelatively positive with respect to the conductors electron-opticallyrelated to the blue strips, then the beam electrons will be subjected toan auxiliary, or micro-, deflection over and above that due to thedeflection providing the raster, so that the lines of impingement ofsuch electrons will now lie within the respective boundaries of the redstrips. Similarly, electrons will strike the blue strips when the wiresassociated with such strips are suitably positive with respect to thered wires. Diiferent component colors of the image are thus displayedaccording to the potential difierence (if any) existing between the twosections of the grid wire assembly.

In designing one grid structure of the above type, the wires aremaintained in position relative to the phosphor strips by means ofspacer elements. The spacing between the plane of the grid wires and thephosphor-coated surface of target is critical in many respects, and mustremain substantially unchanged during operation of the cathode-ray tube.One preferred construction in which the grid wires and the phosphorscreen are formed as a unit is illustrated and described'by theapplicant Renn Zaphiropoulos in his United States Patent No. 2,683,833granted July 13, 1954.

In the Zaphiropoulos assembly, a light-transmissive base plate (whichmay be of glass) is employed as a target backing. This base plate issecured to a grid frame by the strand conductors, or wires, of the grid.A pair of spacer bars is afiixed to one surface of the base plate anddefines a window, or target, area therebetween which may be coated withphosphor strips having the desired color characteristics. Means areprovided for securing the electrically-conducting wires to the frame sothat these wires extend across the window, or target, area of the baseplate and are positioned therefrom by the spacer bars.

Inasmuch as the grid structure being described is designed for colorswitching, or micro-deflection of the beam in the vicinity of the targetelectrode, the Wires or linear conductors are divided in two sets ofalternate strands, and suitable means are provided for applyingpotentials to each set of strands. To carry this out, the frame isdivided into two sections, with each section serving a set of strands.Consequently, in this form of construction, the glass plate issandwiched between the 0 wires of the grid, on one hand, and the twoframe sections, on the other. These two frame portions are pressedtogether by the'tension of the wires associated with the outer frameportion, and this pressure acts to hold the frame, base plate, and wiresin a unitaryassem bly. A suitable insulating means between the twosections of the frame are also provided in order to permit driferentpotentials to be applied to the' two sets of grid Wires.

Under certain circumstances, desirable results may be obtained with acolor structure ofthe nature set forth by dividing the unitary assemblyof grid wires and phosphor plate into two separate sub-assemblies, oneof which is composed of the grid wires and their associated frame (orframes) and the other sub-assembly being composed of the phosphor-coatedplate and its mounting means. One type of construction in which two suchsub-assemblies are employed is set forth in a copending United Statespatent application of Leslie J. Cook and Lawrence Di Quaglia, Serial No.404,03 8, filed January 14, 1954. The structure of the Cook et al.application, however, is intended to be utilized in conjunction with amultiple-gun cathode-ray tube. To adopt this so-calledseparate-plate-from-grid design to a single-gun polychrome cathode-raytube; the construction of the'grid supporting members must be modifiedso that each set of wires may be insulated one from the other.

In the Cook et al. disclosure the grid wire and frame assembly isfabricated as a unit, and the phosphor plate, spacer bars, and mountingelements are fabricated as a second unit. These two sub-assemblies arethen brought together at the proper time so that the wires of the gridassembly fall within notches in the spacer bars associated the plateassembly. Thus a structure results which is similar (as far asoperating. characteristics are concerned) to the unitary design setforth in above-mentioned Zaphiropoulos United States Patent No.2,683,833.

The so-called "separate-plate-from-grid? design, set forth by Cook eta1. may be formed by a grid fabricating method in which the strandconductors are wound around the rectangular grid frame in anuninterrupted fashion. results in two sets, or groups, of parallel wireswh ch lie in different planes. These wires are then forced intosubstantially coplanar relation by means (which include the spacer bars) when the plate assenibly is brought into juxtaposition with the wiregrid.

There is nothing shown by either. Cook et al. which would permit theso-called separate-platerfr'omgrid? design to be used in connection witha color grid. construction in which each set of grid wires is attachedto its, associated frame section by hooking the wire. over a projectionon the frame, laying down the wire across the raster area of the baseplate, hooking it over a projection on the opposite side of the sameframe, bringing it back across the raster area of the base plate, andsoon. This particular back-and-fOrth method of construction may becalled for descriptivev purposes the wrap around design.

"A basic feature of color grid structures of this wrap around type isthat the frame sections are fabricated of conducting material, and thatthe hooks which serve to support the grid wires are cut into twooppositely-disposed edges of each frame section. Thuseach strand of thewire grid directly contacts the frame because of its being wrappedaround the hooks. Consequently, a single electrical contact to the framesection serves as a contact to each one of the strand conductors throughthe material of the frame section itself. Inother words, each of. theseframe sections actually serves as a lead to each strand.

conductor of one set of grid wires. When color switchmg is carried outat, R. F., the R. F. switching current passing through the frame sectioncauses the latter to act as an eflicient radiator of R. F. energy. Inactual.

practice, it has been found that the amount of energy rating such a gridstructure is a prob em all Q. bFFP-E found to constitute a disadvantagetoward the wide ac-- ceptance of such a color-reproducing tube. It is aprinci-- pal feature of the present invention to reduce this radia--tion from the color grid assembly to a point where inter ference withother electronic devices is at a minimum.

According to a feature. of the present invention, a sub stantiallyrectangular grid frame is employed around which a continuous conductoris wound in an uninter-- rupted fashion so as to form a first set ofstrand conduc-- tors having double the spacing desired for the wires ofthefinished grid assembly. second continuous conduc tor is then woundaround a separate support so as to form a further set of strandconductors lying between the conductors formed by the first windingoperation, with each set of conductors being insulated 'fromthe other atpoints where they would normally contact the metal of the frame.Inasmuch as the above design does not comprehend a physical connectionbetween the wire strands and the glass base plate upon which the coloredphosphor strips are deposited, these two members are brought intojuxtaposition so that the individual 'wire'strands are indexed innotches in a pair of spacer bars carried by the glass plate. When theplate (and its support) are secured to the grid frame, complete colorstructure results. All of the operations mentioned above may be carriedout by simple mechanical means thus permitting a relatively low cost ofmanu ture.

One object of the present invention, therefore, is to provide animproved type ofcathode-ray tube designed for the reconstitution ofpolychrome images.

A further object of the present invention is to provide a gridstructure, for cathode-ray tubes designed especially but not exclusivelyfor polychrome image reproduction, in which the various portions of thegrid may be separate ly fabricated and then these portions assembledinto a unitary structure.

A stillfurther object ofthe present invention is to provide a gridstructure, for cathode-ray tubes designed especially but not exclusivelyfor polychrome image reproduction, in which thestrandconductors of thegrid are wound in such fashion that they are electrically insulated fromthe main frame section itself, and, only contactespecially designed.hook strips which are so positioned with respect to the frame sectionthat the former may be readily shielded to thereby minimize undesiredradiation therefrom.

Other. objects and advantages of the present invention will be apparentfrom the following description and from the drawings, in which:

Figure l is a semi-diagrammatic view ofa cathode-ray tube, showing incross-section a color structure in accordance with they presentinvention;

Figure 2. is a plan view of. the color structure of Figure 1 as seenfrom the electron gun end of the cathode-ray tube;

Figure 3 is a detailed view of a portion of Figure 1;

Figure 4. is a perspective view of a portion of Figure 3, showing thedesign of the grid frame itself;

Figure 5 is a perspective view of a portion of Figure 3, showing infurther detail. the manner in which the two sets of grid wiresaresupported by the end pieces of the. frame;

Figure 6 is a perspective view of a part of the entire color assemblyafterthe grid wire sub-assembly and the, base plate sub-assemhly-havebeen brought into proper operating relation;

Figure 7 is a plan view of a portion of the target area of Figure 2,showing one preferred relationship between the gridwires and phosphorstrips;

Figure 8 is a plan view of a portion of Figure 2, showing in additionone manner in which connections may be madefrom the input connector tothe four hook strips of the color structure; and

Figure 9 shows one preferred method in which the hook strips andtheleads from'these hook strips tothe input '5 connector on the cathode-raytube may be shielded so as to prevent excessive R. F. radiation.

Referring now to the drawing, there is shown in Figure l a cathode-raytube certain parts of which are conventional. For example, in the neckend of the tube, and within the envelope 10, there is anindirectly-heated cathode 12 which acts as a source of electrons fordevelopment into a scanning beam. The latter is indicated schematicallyby the trace 14. Adjacent to, and partially surrounding, the cathode 12is a control grid 1, or electrode, 16 suitably apertured to permit thepassage of electrons which are subsequently formed into the beam 14. Thecontrol grid 16 functions in the usual manner to modulate the emittedstream of electrons in accordance with the potential applied theretorelative to the cathode 12. Also in the neck end of the tube there isprovided a first anode or grid 2 (identified by the reference numeral18) to which suitable potensials may be applied so as to result in aninitial acceleration of the electrons emitted from the cathode 12.Adjacent to grid 2 there is provided a second anode, or grid 3(reference numeral 20), for supplying an additional acceleration to theelectrons.

Defiecting coils, comprising a horizontal pair 22 and a vertical path24, are provided for the usual scanning purposes. Obviously the termshorizontal" and vertical are used herein in a descriptive sense only.Thus the electron beam 14 is caused to scan a phosphor-coated target, orlight-transmissive base plate 26, to produce light which is visiblethrough the end wall 28 of the envelope 10.

Shown in Figure 2 is a substantially rectangular support, or frame, 30adapted to fit within the envelope of the cathode-ray tube. This frame30 is made up of a pair of oppositely-disposed L-shaped channel members32, which form two sides of the frame, and a pair of flat end pieces 34,which form the remaining two sides. The L-shaped members 32 arerespectively secured to the end pieces 34 by some suitable method suchas welding. Purely as an example, the side members 32 and end pieces 34of the frame 30 may be fabricated of type #430 stainless steel. Asperhaps best shown in Figure 4 of the drawings, each of the fiat endpieces 34 forms a relatively sharp angle with the plane of the sidemembers 32. Two inserts 36 (one of which is clearly illustrated inFigure 4) are respectively welded or otherwise secured to the two sidemember 32 so as to strengthen the frame and also to form a window area,the outline of which is best seen by reference to Figure 8. This windowhas substantially straight top and bottom edges, and side boundarieswhich are curved in the manner illustrated. A plurality of mountingholes 38 are provided in the flanged portion of each side member 32 soas to permit the color structure to be secured to the inner surface ofthe cathode-ray tube.

Although not shown in the drawing, four tabs, or fingers, are welded orotherwise affixed to the inner surface of the cathode-ray tube envelope10, and extend toward the end wall 28. When the frame 30 is positionedwithin the tube approximately in the location shown in Figure 1, thesefour tabs or fingers will be aligned with the mounting holes 38, andbolts or other securing means (not shown) may be passed through theseholes 38 to best securely mount the frame 30 in position. It might bementioned at this time that it is not necessary to provide electricalinsulation between the frame 39 and the tabs which mount the frame 30 inposition within the cathoderay tube, inasmuch as it will be laterbrought out that the frame 30 may operate at the potential of the conewithout in any way affecting the application of colorswitchingpotentials to the two sets of grid wires. In any event, the particularmeans for mounting the frame 30 within the tube envelope forms no partof the present invention, and any suitable means which rigidly positionsthe frame 30 approximately in the location shown by Figure 1 may beutilized.

It has been brought out above that the present invention contemplatesthe employment of two sub-assemblies, each of which may be fabricatedindependently. It then contemplates that these two sub-assemblies willbe brought together to form a complete color-control structure. Thiswill be later set forth in connection with a description of Figure 6.For the present, however, the construction of the grid wire sub-assemblywill be described-that is, the assembly consisting of the frame 30 andthe two sets of interleaned conductors which extend across the openwindow area thereof.

It has been fully brought out in the above-mentioned ZaphiropoulosUnited States Patent No. 2,683,833, that a continuous filamentaryconductor may be wound backand-forth around a series of hooks wound oneach of two oppositely-disposed edges of a single frame member. In otherwords, each continuous conductor is attached to its associated framesection by hooking the conductor over a projection on the frame, layingdown the wire across the open area of the frame, hooking it over aprojection on the opposite side of the same frame, bringing it backacross the open frame area, and so on. In other words, this constitutesa back-and-forth operation which (with a single filamentary conductor)leaves the parallel wires produced across the window area to have aspacing substantially twice that required in the finished colorstructure. A second continuous conductor is then wound back-and-fortharound the hooks on a second frame section electrically insulated fromthe first frame section. The wires produced by this second winding willlie between the wires produced by the first winding operation, so that agrid structure will result in which the wire spacing is substantiallyequal to that desired for color image reproduction.

A generally similar technique is employed in connection with the gridassembly of the present invention, except that modifications are made inthe particular structure employed to hold the wires in position. As willperhaps best be shown by reference to Figures 3 and 5, the frame endpieces 34 are not notched or grooved in the manner of the frame piecesof the Zaphiropoulos application above referred to, but instead servemerely as a supporting means for those members which actually hold thewires. The actual wire-retaining members of the present invention are inthe form of strips having a generally U-shaped configuration, and areprovided on one edge with a series of hooks adapted to engage each turnof the single filamentary conductor employed to form one set of wires.As will perhaps be best shown by Figure 3, there are two hook strips foreach end piece 34, a first inner strip and a second outer strip. Eachinner hook strip has its open end slipped over the projecting edge ofone of the end pieces 34 after a layer of insulating material 40 hasbeen laid over both those surface portions of the end piece which thefirst inner hook strip is designed to encompass. Each inner hook strip42 extends for the entire length of its respective end piece 34 from oneof the L-shaped side members 32 to the other L-shaped member 32. Inother words, each inner hook strip 42 takes the place of the hooks whichwere actually out into the material of the frame section itself in theabove-mentioned Zaphiropoulos assembly. It will be noted, especiallyfrom Figure 3, that when the wire is hooked over one of the projectionson the inner hook strip 42, then the continous filamentary conductor,which forms the first set of wires 44 (Figure 5) will exert a pulling"action upon the hooks of the strips 42 which acts to pull the latterdown more tightly upon the upper edge of their respective end pieces.Thus the tension of the first set of wires 44 acts to hold the innerhook strips 42 tightly compressed against the outer edge of theirrespective end pieces 34 through the insulating layers 40 which arepresent therebetween. The first winding operation with the firstfilamentary conductor is thus completed so that a set of wires 44extends in substantially parallel coplanar relationship across-thewindow area of the frame 30.

When his first win ing operati n has been accomplished, a furtherinsulating layer is placed o er the ou r su fa f ach of he two hock r p42 h u insulating layer is designated in Figures 3 and 5 by thereference numeral 46. On top of each insulating layer 46 an outer hookstrip 48 is placed, these outer hook strips 48 having the same generallyU-shaped configuration as the inner hook strips 42, and being providedwith a series of hooks on that edge associated with the hooked ed o e chnn r strip 42 Th s cond continuous fi amentary conductor is then woundback-and-forth around the hooks on these outer strips 48 so as to resultin a second Set of linear conductors 50 lying between the first set ofconductors 44, with the two sets of hook, strips being insulated fromone another by the presence of the insulating layers 46. As best seen byreference to Figures 3 and 5, each outer hook strip 48 is isolatedelectrically from its associated inner hook strip 42 and also from theframe section by means of the two insulating layers 49 and 46. Thus theelectrical potential of the frame 30, as will be shown below, has nobearing upon the potentials that may be applied to the hook strips 42and 48 and hence to the two sets of grid wires 44 and 50.

Due to the angular relationship between the frame end pieces 34 and theL-shaped side members 32, the tension of the grid wires 44 and (asexerted through the hook strips 42 and 48) acts to maintain these stripstightly wedged against their respective end pieces 34,, and prec udesany possibility that the hook strips will slip off the end pieces 34 andthus render the cathode-ray tube inoperative. Furthermore, each of thehook strips 42, and 4,8 acts as an electrical lead to each one of thelinear conductors 44 and 50 associated therewith, and, since the hookstrips have a relatively low electrical resistance, identical potentialsmay be applied to all of the wires of each of the two sets.

Purely as an example, the frame 30 may have approxi: mately 400 linearconductors extending across the open window area thereof, 200 of thesebeing associated with the inner hook strips 42 and the remaining 200.being associated with the outer hook strips 48. These two sets of wiresmay be, respectively, formed from. two. contin uous filamentarystainless, steel conductors of approximately .006" diameter.

In order to prevent electrical contact between the conductors 44 and5,0. as they pass over the. respective edges of the end pieces 34 priorto extending across the, window area of the frame 30, and also to,insulate each set of conductors from the frame itself, the outer edge ofeach frame piece 34 is recessed in such a manner as to receive anelongated insulating element preferablyhaving the form of one of theglass rods 51 and 52 Each such rod is provided with a series ofprecisely-formed grooves, with the distance between the grooves beingequal to the distance desired between adjacent conductors 44. and 5.01.

of the finished color structure ,(see Figure 6.). It will be notedespecially from Figures 3 and Sthat if therecess formed in each oftheend pieces 34 is of proper configuration, the pressure or tension of thewires 44 and 50 will act to hold the grooved insulators. in theirrespective recesses in the end-pieces 34 without any such securing meansas cement. The structure disclosed is thus. extremely resistant todamage byshocks of a physical nature suchas may, occur during. handlingor transportation ofv of the cathode-ray tube. One substance which hasproven.

to be satisfactory in practice, comprises resilient insulating tape of avitreous, nature.

Although in sorneinstances ,thehook strips, 42 and 48.:- may, themselvesserve as leadsto eachof-the. individual:- conductons, 4,4,; and-,5!)ofthe, wire grid. assembly, ithas.

become. customer-yin practice to'em'pioy a separate electrical leadwhich extends throughout the length of each of the hook strips. Eachsuch lead, which may be a strip of very thin aluminum, is placed betweeneach of the hook strips and the insulating layers 40v and 46 so that anelectrical potential may be applied to each of the hook strips 42 and 48which 'is independent of the potential of the frame 30. These electricalleads may be of a design as shown in Figure 5, where the ends of two ofthe leads are shown as extending beyond the frame end pieces 34.Furthermore, by employing integral leads of this nature, it isunnecessary to make a connection between separate input leads and eachof the hook strips 42 and 48.

Although a back-and-forth winding operation satisfactory in principlefor producing the grid of the present invention has been fully set forthin the above-mentioned Zaphiropoulos United States Patent No. 2,683,833,neverthe less it might be helpful to state herein that, following theplacing on their respective. end pieces 34 of the inner insulatinglayers 40, the inner hook strips 42 and the lead strips A, the winding.process begins by attaching the end of the first continuous filamentaryconductor to a hook at the extreme end of one of the hook strips 42. Thefirst set of grid wires 44 is then wound preferably by rotating theframe structure 3.0- sov that the wire starting from the hook justmentioned goes around the first grooved glass insulator 51, extendsacross the window area of the frame 30, falls in the appropriate grooveon the other grooved insulator 52, and is wound around the extreme endhook on the opposite one of the inner hook strips 42. At this point, thedirection of rotation of the frame 30 is reversed, and the windingprocedure continues in a similar manner until the first set of gridwires 44. is obtained. The second insulating layer 46 is then placedover the inner hook strip 42, the lead strips B placed over theinsulation 46, the outer hook strips slipped over the lead strips B, andthen the second set of grid wires. 50 wound in the same manner as thatdescribed above so as to result in two interlaced sets of grid wiresacross the window area of the frame 30. It will be clear that all of thehook strips, leads, and grooved cane pieces, 51 and 52 are held firmlyin place by the tension of the wires 44 and 50. Furthermore, it willalso be evident that eachof'the hook strips 42 and 48'is insulatedelectrically from the. frame 30 as well as from the other hook strip,and that the leads A and B to each of the four hookstrips will haveextending portions (indicated best in Figures 5 andn9).

The light-transmissive backing or base plate 26 carries on one of itssurfaces. a seriesv of phosphor strips laid down in a manner such aswill be described in connection 4 with Figure 7. That is, the sequenceof these phosphor strips may be, for. example, red, green, blue, green,red, green, and so on. For proper operation of the tube being described,it is desirable that each of the strand conductors of thegridbealigned,in an electro-optical sense, with the red and blue phosphor strips. Tobring. this about, a pair of insulating spacer elements, or bars, 54 aresecurely aflixed to one surface of the base plate 26 in, a manner bestshown in Figuresl, 3 and 6. These spacer bars, as well as the. baseplate 26, may comprise boro-silicate glass, but-in any event shouldhave. the same coefficient of expansion. These spacer bars S-tperformthe dual function of aligning the coplanar wirestrands with. thephosphor strips, and also maintain the, wire strands at a uniformdistance from the surface of thebase Plate 26.

The base plate 26, with its pair of spacer bars 54, is mounted relativeto the frame 30so that it occupies the position best shown in Figures 3.and 6. Referring to the latter figure, a pair of plate anchoring bars56 (one only being illustrated) extend across that surface of thephosphor-coated base plate 26 opposite to the side which is coatedwiththe phosphor and which carries the spacer bars 54'. In other words,the plate anchoring bars 56ex tend across that surface of the base plate26 nearest to charging current to the grid wires.

- plate anchoring bars 56 serve the purpose of positioning the plate 26,and each bar 56 is associated with a pair of anchoring arms 58. Theseanchoring arms 58 are each of substantially Z-shaped configuration, andare designed to have one projecting portion secured to the plateanchoring bar 56 and the other projecting portion secured to one of theframe side members 32. When the anchoring arms are secured in positionby spot-welding or other means,

the phosphor plate 26 is precluded from movement relative to the frame30 by means of the pressure of the plate anchoring bars 56 on thesurface thereof, which pressure is maintained by the anchoring arms 58.

When the phosphor-coated base plate 26 is brought into its desiredposition relative to the frame 30 (as best shown in Figure 6), the gridwires of the two sets 44 and 58 will fall within appropriate groovescutinto the upper edge of each spacer bar. These grooves are similar tothose out into the outer edge of each of the insulating members 51 and52, so that the alignment of the wires, initially brought about by theinsulating members 51 and 52, is enhanced and maintained by the groovesof the spacer bars. As a result of these two aligning means, the spacingof the wires as they extend across the open area of the frame 38 ismaintained substantially constant during operation of the cathode raytube.

The relative position of the individual conducting strands, or gridwires, and the red, green and blue phosphor strips which are applied tothat surface of the base plate 26 impacted by the electron scanning beamis shown in Figure 7. Although the particular arrangement of thephosphor strips forms no part of the present invention, nonetheless adesirable arrangement has been shown to consist of a sequence of stripssuch as red, green, blue, green, red, green, and so on. The strip widthsare chosen in accordance with tube design so as to provideelectrooptical rather than physical relationships between the grid wiresand the phosphor strips. Each adjacent pair of grid wires is accordinglydesigned to subtend (in an electro-optical sense) a portion of thetarget electrode surface which includes phosphor areas of each of thecomponent colors. Generally speaking, however, it may be said that thedistance between adjacent grid wires is substantially equal in onedimension to a single elemental area of the image to be resolved by thecathode-ray tube.

it has been stated above that one of the principal objects of thepresent invention is to reduce the amount of radiation produced by acolor structure of the type being described to a point which is withinlimits which have been designated as being commercially acceptable. Inthis connection, it has been found to be unnecessary to shield the gridwires themselves, inasmuch as radiation from the latter is almostnegligible. This is because each grid wire carries only an extremelysmall fraction of the charging current, and, since this current is inopposite directions in adjacent wires, field radiation is effectivelycancelled from this portion of the assembly. The principal source ofradiation is in the frame structure itself, since the latter ordinarilyserves as a lead to carry the However, the disclosure of the presentinvention does not make the grid frame part of the circuit which carriesthis charging current, and hence the grid frame as a unit need not beshielded. The only effective shielding necessary is that around theleads from the input terminal of the cathoderay tube up to and includingthe point where the charging current is fed to each one of the gridwires.

it has been stated above that the electrical circuit embracing theseelements includes only the inner hook strips 42, the outer hook strips48, and the two lead strips A and B which carry the charging currentfrom the input terminal ofthe cathode ray tube to the hook strips '42and 48 and hence to the grid wires 44 and 50. Referring now to Figure 8,it will be seen that if shielding is provided from the input coaxialconnector 60 of the cathode ray tube along the leads A and B, and overand encompassing the outer hook strips 48, then the amount of undesiredradiation from the cathoderay tube will be materially reduced.

One preferred method of accomplishing the above objective is to provideapair of end shields (best shown in Figure 8 and identified by thereference numerals 62 and ed) and a single side shield 66. The detailsof one end shield 62 and of the side shield 66 are best shown in Figure9. Reference to this latter figure shows that each end shield (both endshields are identical) is composed of an inverted U-shaped open-endedsheet-metal member which is siipped 'over'one of the outer hook strips48 in the manner shown in the drawing. This end shield surrounds all ofthe outer surface of its associated hook strip in the manner shown, andof course is spaced therefrom so as to have no electrical contacttherewith. This end shield extends for the length ofthe hook strip andconsequently for the length of the associated frame end piece 34. Eachend shield is provided along one of its edges with a flanged projectingportion 68 (Figure 9) which lies flat against the surface of one of themembers 36 (see again Figure 8) which faces the electron gun of thecathode-ray tube After the end shield 62 (for example) is placed in theposition best shown by Figure 9, the flanged portion 6% thereof issecured to the surface of the member 36 by some preferred method such asspotwelding; The purpose of this operation is to hold the end shield 62spaced apart from the outer hook strip 48 so as to contain the lattersubstantially within its confines as best shown in Figure 9;Substantially all radiation from the hook strips 42 and 48 is thusprevented from extending beyond the end shields, inasmuch as the latterare directly connected both physically and electrically to the frame 30which in itself carries no color-switching potentials.

However, since the leads A and B do carry the colorswitchingcurrents,'it is'desirable that these leads be shielded throughout theirlength, and this is accomplished in part by the side shield 66. Thisside shield 66, as best shown in Figure 9, is of hollow tubularconstruction (although it may be somewhat rectangular in cross-section),and extends from the point Where the leads A and B from the coaxialconnector 60 enter the vicinity of the frame side member 32 upapproximately to those points where these leads come in contact withtheir respective hook strips 42 and 48. Actually this side shield 66, asshown in Figures 8 and 9, may be composed of a single tubular memberextending substantially throughout the length of one frame side member32. Atits center point, one of its surfaces is cut open (as again bestshown by Figure 9) so as to form a.middle outlet through which the twosets of leads A and B may be passed.

The side shield 66 may be secured to the frame side member 32 in anysuitable manner, such as by a pair of steel brackets 70 one of which isshown in Figure 9. Each steel bracket may again be spot-welded (as shownat '72, for example) to the frame side member 32. Obviously the leads Aand B must be kept out of electrical contact with the side shield 66,inasmuch as the latter is at frame potential, but since the leads arecomposed of material (such as aluminum) having a fairly rigid nature, itis possible to maintain them in somewhat of a central position withrespect to the shield surfaces.

Both the two end shields 62 and 64, as well as the singe side shield 66,may be formed of aluminum sheet, while the brackets 70 are preferablycomposed of some material such as stainless steel.

If it is found that excessive radiation results from the leads A and Bfrom the point where they emerge from the coaxial input connector 60 upto the point where they enter the side shield 66 ,(as best shown inFigure 8) r 11 it is obviously possible to place another flexiblealuminum shield (not shown) over the leads A and B throughout thisdistance.

It has been found in practice that in some cases currents may be inducedin the frame when R. F. switching potentials are fed to the grid wires44 and through the leads A and B. If these induced currents becomeexcessive, it is possible to place a sheet of aluminum foil over the twosurfaces of each of the end pieces 34 (Figure 4) before the first layerof insulation 40 is placed over the outer edges of these frame pieces.This results in an appreciable reduction in the induced currents in theframe, and may, in some cases, have a marked effect upon the switchingpower requirements.

In summary, therefore, a few of the outstanding featur'es of the designdescribed above are that it appreciably reduces the amount of R. F.radiation from the color structure and hence reduces the amount ofinterference with other electronic apparatus in the neighborhood of thecathode-ray tube; it permits a greater usable area for viewing thereproduced image, inasmuch as the frame and pieces are at an angle tothe plane of the grid wires rather than substantially parallel theretoas has been the case in previous tube constructions; it involves fewerexpensive silver-plated parts, and hence the tube of the presentdisclosure may be constructed at lower cost; the shielding structureemployed herein is simple in design and can be added to the colorassembly with very little additional effort; and, finally, use of theso-called separate-plate-from-grid design permits these twosub-assemblies to be fabricated at dilferent locations with a consequentsaving inproduction cost. Furthermore, any defect in either of the twosub-assemblies will not necessitate discarding the entire color unit.

Having thus described the invention, what is claimed is:

1. Ina grid structure designed for incorporation into a cathode-ray tubeadapted to reconstitute images in a plurality of colors, the combinationof a grid-carrying frame composed of a pair of oppositely-disposed sidemembers and a pair of oppositely-disposed end pieces, defining, withsaid side members, a frame window area, said pair of end pieces beingof-generally fiat configuration and being respectively secured to saidpair of side members so as to form an angle in the range between zeroand 90 with the plane defined by said side members, a layer ofinsulating material covering the outer edges and at least a portion ofeach surface of each of said pair of frame end pieces, a pair ofU-shaped strips respectively overlying the outer edges of said pair offrame end pieces and also said insulating layer, and a plurality oflinear conductors supported by said strips so as to lie across thewindow area of said frame in substantially parallel alignment.

2. In a grid structure designed for incorporation into a cathode-raytube adapted to reconstitute images in a plurality of colors, thecombination of a gridcarrying frame composed of a pair' ofoppositely-disposed side members and a pair of oppositely-disposed endpieces. defining, with said side members, a frame window area, said pairof end pieces being of generally flat configuration and beingrespectively secured to said pair of side members so as to form an angleof between zero and 90 with the plane defined by said side members, alayer of insulating material surrounding the outer edge of each of thesaid pair of frame end pieces and at least a portion of each surfacethereof, a-pair of U-shaped retaining strips, respectively. overlyingthe outer edges-of said pair of frame end pieces as well as saidinsulation, a second layer of insulation overlying the outer surface ofeach of the said pair of retaining. strips, asecondpair of. U- shapedretaining; stripsoverlying; thewlast-mentioned insulating.layers,, afirst set:of linearconductorsv supported by; saidwfirst-mentioned painof.v U-shaped' retainingstrips so aszto lie. across-the windows area ofsaid'frame in sub-- stantially parallel fashion, and a second set oflinear conductors supported by said second pair of U-shaped retainingstrips so as also to lie across the window area 5 of said frame insubstantially parallel fashion with the linear conductors supported bysaid first strip lying intermediate the linear conductors supported bysaid sec- I applying potentials to the said two pairs of strips "which"are different from the potential of said frame includes means forinsulating each of the said sets of linear conductors from said frame,said last-mentioned means including a pair of insulating rods ofvitreous material respectively receivable in a pair of recessesrespectively formed along the edges of each of said pair of flat endpieces opposite to those edges overlaid by said retaining strips, thesaid linear conductors passing over a portion of the surface of each ofthe said pair of insulating rods in such a manner as to be kept fromelectrical contact with said frame.

5. In a grid structure designed for incorporation into a cathode-raytube adapted to reconstitute images in a plurality of colors, thecombination of a grid-carrying frame composed of. a pair ofoppositely-disposed side.

members and a pair of oppositely-disposed end pieces defining, with saidside members, a frame window area, saidpair of end pieces being ofgenerally flat configuration and being respectively secured to said pairof side members, a pair of retaining strips respectively overlying theouter edges ofsaid pair of frame end pieces, a sheet of insulatingmaterial between each of said pair of retaining strips and itsassociated frame end piece so as to electrically insulate eachof saidstrips from its associated frame end piece, and a pair ofradiation-suppressing members formed of sheet-like material at leastpartially surrounding each of said retaining strips and spaced aparttherefrom, said pair of radiation-suppressing members being securedalong oneedge thereof to a surface of said frame in the vicinity of saidretaining strips.

6. In a grid structure designed for incorporation into a cathode-raytube adapted to reconstitute images in a plurality of colors, thecombination of a grid-carrying frame composed of a pair ofoppositely-disposed side members and a pair of oppositely-disposed endpieces defining with said side members a frame Window area, said pair ofend pieces being of generally fiat configuration and being respectivelysecured to the said pair of side members so as to lie at'an angle intherange between zero and to the plane defined by said sidemernbe'rs, alayer of insulating material respectively surrounding the outer edge ofeach of said pair of frame end pieces and at least a portion ofthe'surface thereof, a Ushaped hook strip overlying each saidinsulating-layer, a second insulating layer overlying the outer surfaceofeachof said pair of Ushaped hook strips, a second pair of U-shapedhook strips respectively overlying the said last-mentioned insulatinglayers, a first continuous conductor wound back-'and-forth betweencorresponding hookson said first pair of U-shaped hook strips so as tolie across the window area of said frame in the form of a plurality oflinear conductors substantially parallel to one another, a'secondcontinuous conductor wound b'ack-and-forth between correspondingindividual hooks onsaid last mentioned pair of U-shaped hook strips soas to lie'across' the' window area of said frame" in a form ofaplurality of linear conductors substantially parallel to one another andlying intermediate the individual'conductors associated withsaid firstU-shaped l'ioolc strips -means' for insulating thelinear conductorsformed by the said two winding operations from the metallic materialcomprising said frame, and a pair of radiation shields respectivelysurrounding the said second pair of U-shaped hook strips and spacedapart therefrom, each of the said pair of radiation shields beingaiiixed to a surface of said frame which is electrically insulated fromeach of the two pairs of U-shaped hook strips by at least one of thesaid layers of insulating material.

7. The combination of claim 6, further comprising conducting leads toeach of the said two pairs of hook strips, whereby potentials may beapplied to each of the said two pairs of hook strips which are differentfrom the potential applied to said frame.

8. The combination of claim 7, further comprising a tubular shield forthe leads to each of the said two pairs of hook strips, said tubularshield substantially completely enclosing the two pairs of leads for atleast a portion of their length and being respectively secured to one ofthe said pair of oppositely-disposed frame side members, said tubularshield having an opening substantially intermediate thereof to permitemergence of said leads.

9. In a grid structure designed for incorporation into a cathode-raytube adapted to reconstitute images in a plurality of colors, thecombination of a grid-carrying frame composed of a pair ofoppositely-disposed side members and a pair of oppositely-disposed endpieces defining, with said side members, a frame window area, said pairof end pieces being of generally fiat configuration and beingrespectively secured to said pair of side members so as to lie at anangle in the range between zero and 90 to the plane defined by said sidemembers, an insulating layer overlying at least a portion of the surfaceof each of said pair of end pieces, a pair of U-shaped hook stripsrespectively overlying said insulating layers, a second insulating layeroverlying each of the said first U-shaped hook strips, and a second pairof U-shaped hook strips respectively overlying said second insulatinglayers so as to be electrically insulated from said first pair ofU-shaped hook strips and also from the said pair of frame end pieces, afirst continuous conductor wound back-and-forth between correspondingindividual hooks on said first pair of U- shaped hook strips so as tolie across the window area of said frame in the form of a plurality oflinear conductors substantially parallel to one another, a secondcontinuous conductor wound back-and-forth between corresponding hooks onsaid second pair of U-shaped hook strips so as to lie across the windowarea of said frame in the form of a pluraiity of linear conductorsinter-leaned with the conductors associated with said first-mentionedU-shaped hook strips, electrical connections to each of the said hookstrips, a phosphor-coated base plate, a pair of spacer bars respectivelysecured near opposite edges of said phosphor coated base plate, andmeans for bringing said plate into juxtaposition with said frame so thateach of said spacer bars contacts the said interleaned conductors,thereby maintaining said conductors substantially equidistant from thephosphor coating on said base plate across the frame window area.

10. The combination of claim 9, in which each of said spacer bars isgrooved at spaced points along its outer edge, with the said interleanedconductors respectively falling within the said grooves.

11. The combination of claim 10, in which a U-shaped 14 shielding memberoverlies each of the said pair of outer hook strips throughout itslength and is spaced apart therefrom, each of the said pair of shieldingmembers being respectively secured to a surface of said frame adjacentto one of the said pair of end pieces.

12. The combination of claim 11, in which leads are provided to each ofthe said two pairs of hook strips, further comprising a shielding memberfor said leads in the form of a hollow tube enclosing said leads for atleast a portion of their length and respectively secured to one of theside members of said frame.

13. In a grid structure designed for incorporation into a cathode-raytube adapted to reconstitute images in a plurality of colors, thecombination of a grid-carrying frame composed of a pair ofoppositely-disposed side members and a pair of oppositely-disposed endpieces defining, with said side members, a frame window area, said pairof end pieces being of generally flat configuration and beingrespectively secured to said pair of side members so as to lie at anangle other than zero to the plane defined by said side members, aplurality of linear conductors arranged side-by-side in substantiallyparallel relationship, means for supporting said plurality of linearconductors by said pair of end pieces so that the former extend acrossthe window area of said frame in essentially coplanar fashion, andfurther means for precluding electrical contact between said frame andeach conductor of the said plurality.

14. In a grid structure designed for incorporation into a cathode-raytube adapted to reconstitute images in a plurality of colors, thecombination of a grid-carrying frame composed of a pair ofoppositely-disposed side members and a pair of oppositely-disposed endpieces of generally fiat configuration defining, with said side members,a frame window area, a plurality of linear conductors arrangedside-by-side in substantially parallel relationship, means forsupporting said plurality of linear conductors by said pair of endpieces so that the former extend across the window area of said frame inessentially coplanar fashion, means for precluding electrical contactbetween said frame and each conductor of the said plurality, means forconnecting each conductor of the said plurality to a source of energy,and means for shielding at least a portion of said last-mentioned meansto reduce undesired radiation of energy therefrom.

15. A grid structure according to claim 14, in which said means forconnecting each conductor of the said plurality to a source of energyincludes a strip of electrically-conducting material extendingtransversely of the said parallel conductors and lying adjacent to butspaced apart from the surface of one of said frame end pieces, and inwhich said shielding means includes a metallic member at least in partenclosing said strip, said metallic member being supported by said frameand operating substantially at the electrical potential of the frame.

References Cited in the file of this patent UNITED STATES PATENTS2,416,056 Kallmann Feb. 18, 1947 FOREIGN PATENTS 521,407 Great BritainMay 21, 1940 878,316 France Jan. 18, 1943

